The invention relates to a palladium- and copper-free high-gold-content dental alloy, in particular a fire-on dental alloy, for the production of dental prostheses such as dental crowns, bridges, inlays, or onlays, containing at least platinum and at least one particle refiner.
Alloys free of palladium and copper, so-called bio-alloys, are especially used for sensitive patients. The disadvantage of these alloys is the low mechanical stability, especially during ceramic firing, compared to those high-gold-content dental alloys that contain palladium and copper. It must be noted that these particular palladium- and copper-free alloys are prone to distortions. These are caused by so-called creeping of the alloy at high temperatures, the creeping being localized at the particle boundaries.
To achieve increased high temperature stability of Pd—Cu-free high-gold-content dental alloys, one desires precipitation at the particle boundaries. Principal constituents of the precipitation phase contain high-melting elements, with no significant measurable gold content in the precipitation. Platinum is prone to undefined precipitations, which manifest themselves in an inhomogeneous distribution of the phase and in undefined morphology. In extreme cases, this leads to the formation of so-called “stars”. Independently of this, distortions arise because of undefined precipitation. Also affected are polishability and millability of the alloy. The optical appearance is affected as the golden color of the alloy fades.
EP-A-1 193 320 discloses a fire-on high-gold-content dental alloy, which contains 80.0 to 86.5% gold, 7.1 to 13% platinum, 0.1 to 8% palladium, 0 to 1.2% silver, 0.7 to 3.5% zinc, 0.0 to 1.0% iron, iridium, ruthenium, rhodium, tantalum, manganese, rhenium, niobium, 0 to 3.5% tin, indium, gallium or 0 to 0.5% copper. A drawback of this particular alloy is its palladium content, which precludes use a bio-alloy.
U.S. Pat. No. 5,423,680 describes a dental alloy, which is free of palladium, gallium, and copper, and possesses a high thermal expansion coefficient. The alloy can contain 50 to 75% Au, 8 to 9% Pt, 12.4 to 38% Ag, 2% In, 1 to 2% Mn, 4% Sn, 1 to 1.9% Zn, 0.05% Ir, and 0.05% CaB6. Platinum, niobium, and tantalum are mentioned as further ingredients.
A noble metal dental alloy in accordance with DE-A-31 32 143 contains 70-80% gold, 1-10% platinum, 5-15% palladium, 0.1-5% tin, 0-5% indium, 0-2% zinc, 0.1-9% silver or copper, 0.0-2% iridium, rhenium, or ruthenium, as well as 0.1-3% cobalt, chromium, gallium, molybdenum, niobium, tantalum, or vanadium.
DE-A-100 33 445 describes a high-gold-content dental alloy that can be copper-free. In accordance with example 1, the alloy is composed of 77.6 wt. % gold, 19.6 wt. % platinum, 2.1 wt. % zinc, 0.6 wt. % tantalum, and 0.1 wt. % iridium.
A high-gold-content alloy in accordance with DE-A-27 46 525 contains a maximum of 0.8 wt. % tantalum and a minimum of 0.5 wt. % rhodium.
DE-A-24 24 575 describes a fire-on gold alloy, which in addition to 80 to 90 wt. % gold, 5 to 15 wt. % platinum, 0.1 to 2 wt. % In, 0 to 2 wt. % tin and 0.05 to 0.5 wt. % Ir also contains 0.5 to 3 wt. % rhodium. Instead of or in addition to rhodium, 0.1 to 2 wt. % tantalum and/or wolfram may be present.
A fire-on gold alloy in accordance with U.S. Pat. No. 4,062,676 contains 60%-90% Au, 5%-35% Pt, 0.1%-3% In, 0%-10% Pd, 0%-3% Sn, 0.5%-3% Rh, 0.1%-2% Ta and/or W, and 0.3%-2% Zn, whereby the weight ratio of the metals of the platinum group relative to zinc, and relative to Ta and/or W is 15-30:1:0.5-1.3.